Spotted owls meet new challenge in Sisters

Bill Bartlett | Last updated Jun 25, 2024 9:32am0

Already burdened by diminished habitat, the few remaining spotted owls around Sisters are faced with a new threat: their family relative, the barred owl. The barred owl (Strix varia) is the eastern cousin to our western spotted owl (Strix occidentalis). Like the spotted owl, the barred owl lives in forests, hunts at night, and feeds largely on small mammals.

They differ in that the barred owl is more of a generalist, opportunistic predator (feeding also on crayfish, snakes, even small birds and insects), has a broader habitat tolerance, and is slightly larger and more aggressive than the spotted owl.

In the last 100 years, barred owls have gradually extended their range westward, and around 1959, they began to formally "invade" the spotted owl's range in British Columbia. By the 1970's, barred owls were documented in Washington and Oregon.

With possibly fewer than 100 spotted owls in all of the Deschutes National Forest, biologists are worried by the proliferation of the barred owl. Sisters has lost most of its spotted owl habitat as a result of wildfire.

There are no definitive numbers but most estimates are in the range of 2,000 remaining breeding pairs in the Northwest.

The barred owl is crowding out the less aggressive northern spotted owl according to the USFWS (U.S. Fish & Wildlife Service). To ensure the survival of the spotted owl, a threatened species, the service is proposing the mass removal of over 470,000 barred owls across California, Washington, and Oregon over a three-decade span.

Conservationists and animal welfare advocates are debating the moral issue of killing one species to protect another. District Ranger Ian Reid does not envision any such action in the Sisters District.

Keeping an eye on owls is routine - among many other tasks - for Forest Service district biologists, Laura McMahon and Liz Day. The Nugget accompanied them recently as they set out audio traps where computer modeling told them spotted owls may be present. Trapped, as in capturing sound waves, not the owls themselves.

Photo by Bill Bartlett

Forest Service biologists Laura McMahon and Liz Day are using technology to monitor for spotted owls in the forest near Sisters.

"Their range is only about 1.2 miles," McMahon said.

That's miniscule in a vast forest, so finding them is akin to finding a needle in a hay stack. Day and McMahon patiently explained the ideal habitat as they traipsed about looking for just such locales. "They are very sensitive to heat," Day pointed out. Indeed, when the air suddenly dropped noticeably and when the cover changed from mostly ponderosa to mixed conifers, it was right where computer maps suggested.

Now to find the perfect tree on which to attach a high tech listening device. Lauren DuRocher, environmental coordinator, watched as the pair carefully calibrated the device, recorded its precise location, and attached it to the tree, wiping away any traces of human scent.

Northern spotted owls have been the center of controversy for three decades between environmentalists and the timber industry. Mapping and census taking of the owls is just one facet of healthy forest management DuRocher details. As a listed threatened species, DuRocher and her team have to consider any disruptions to its habitat when evaluating projects from recreation siting to harvesting.

The Forest Service thinks in decades, whereas forest users tend to view the forest as it is on any given day.

Speed is seldom a feature of Forest Service projects, often delayed by opposition. The Green Ridge restoration project near Camp Sherman is a prime example. The scope-of-work began seven years ago and implementation is tentatively scheduled for start in September.

Typical of competing interests, opponents are disturbed by the resulting sale of removed timber. The agency lists six priorities for the project including bolstering habitat for northern spotted owls and mule deer, favored by many of the same in opposition.

The debate over the spotted owl, beginning in the 1980s with wide media coverage across the country, led to hostilities in some Pacific Northwest's small towns. Though the issues were more complex, many reported the controversy as a struggle between loggers' jobs and protection of the owls' ancient forest habitat.

Photo by Bill Bartlett

Computer modeling and monitoring helps give a picture of owls' true status in local woods.

McMahon and Day typify the front line work of healthy forests. McMahon is a Supervisory Wildlife Biologist with a M.S. Natural Resources at University of Idaho (Moscow) and B.S. Fisheries and Wildlife Science at OSU (Corvallis). Her background includes working for U.S. Fish and Wildlife Service, Wisconsin Dept. of Natural Resources, National Park Service, and California Dept of Fish and Wildlife.

Day holds a B.S. in Wildlife Ecology and Conservation; Agriculture and Natural Resources at University of Delaware. She has worked for the Forest Service since 2018 as a Fisheries or Wildlife Technician at several Ranger Districts in the Northwest.

ARU captures spotted owl in Sisters

Bill Bartlett

The northern spotted owl was listed as threatened in 1990. In 2023, the U.S. Fish and Wildlife Service proposed upping its assessment. The owl faces multiple threats including large, extremely hot wildfires that char the bird’s preferred habitat and nonnative barred owls that outcompete the spotted owl for territory and food.

The northern spotted owl is one of the most studied birds in the world. Monitoring spotted owl populations throughout the species’ range in Washington, Oregon, and California is an extensive effort conducted among several agencies. These efforts are not designed to count the number of individual spotted owls but rather to gather sampling data from which population trends are derived.

Sisters Ranger District biologists are deploying autonomous recording units, or ARUs, across the landscape according to a hexagonal grid design to aid in this effort. In 7-8 hexagons at a time, they’ll place up to four ARUs/hexagon, for six-week deployment to monitor spotted owls. After the deployments, ARU recordings are taken back to District Headquarters for analysis. They’ll use software that’s been trained to scan the audio files for up to 40 different bird species, including barred and northern spotted owls.

“We have the technology right in the office,” said Laura McMahon, Supervisory Wildlife Biologist. “We do not have to send it to a lab for analysis.”

Prior to ARU’s, biologists like McMahon would have to go out at day’s end into the night and call the owls with a mouth piece. While it might be successful it also drew the attention of barred owls who could then take over the spotted owls’ limited territory.

Liz Day, district wildlife biologist, explained how extremely accurate the units are, able to distinguish between dozens of different sound waves such as from other animals, wind, rain, and a host of acoustical interference.

A primary example is the K. Lisa Yang Center for Conservation Bioacoustics at the Cornell University Lab focused on the detection and classification of avian sounds using machine learning (AI) to assist experts and citizen scientists in their work of monitoring and protecting birds. BirdNET is a research platform that aims at recognizing birds by sound at scale.

McMahon and Day retrieve the data cards from the ARU’s and within days can produce the equivalent of months of work. From the results they can predict with a high degree of probability where owls are.

“A barred owl produces a distinctly different sound than a spotted owl,” said Day, noting that for the human ear it can be difficult to distinguish.

The same technology is used by other biologists to monitor various species. In Sisters County ARU’s are routinely deployed to capture wolf activity. Like humans, every wolf has a unique voice print.